_Distribution._ The most widely spread genus, _Cycas_, occurs in Siam, India, the Nicobar Islands, Ceylon, Madagascar, and Australia, in many of the islands in the Indian and Pacific oceans, in New Guinea, Borneo, New Caledonia, New Britain, China and Japan[25]. _Zamia_, the most northerly genus, extends from North Mexico and Florida through Central America and some of the West Indian islands to Ecuador, Bolivia, Chile, and Peru. _Dioon_ and _Ceratozamia_ are confined to South Mexico, and _Microcycas_ flourishes on the Cuban mountains. The continent of Africa possesses two endemic genera _Encephalartos_ and _Stangeria._ _Encephalartos_ extends from Cape Colony through Natal and Zululand to Zanzibar and Mombasa[26]: a specimen in the Kew Herbarium (probably _E. Hildebrandti_) is said to have been collected as far north as the Soudan. Two species are recorded from the Congo[27] and _E. Barteri_, discovered by Barter in Central Africa, is recorded from the Gold Coast[28]. _Stangeria_ has a much more limited range in S.E. Africa[29]; Australia possesses _Macrozamia_, represented by several species in Western Australia, New South Wales and Queensland, _Cycas_ in Queensland and the Northern territory and the Queensland genus _Bowenia_. There are no Cycads in New Zealand. As a whole Cycads have a limited range and with the exception of _Cycas_ and _Zamia_ none of them extend beyond the limits of a single continent. They are as a rule not gregarious plants and play a subordinate part in the facies of the vegetation. _Macrozamia_ forms dense thickets[30] in some districts and occurs both in exposed situations and in association with Palms in damp Queensland forests. Chamberlain[31] speaks of 100 plants of _Dioon edule_ as visible in one view in South Mexico where the species forms a mountain forest. In Florida _Zamia pumila_[32] grows in dense moist woods, a habitat in contrast to that of many Cycads. The Mexican _Ceratozamia_ is associated with luxuriant vegetation, while its compatriot _Dioon_[33] lives in blazing sunshine. Sir Joseph Hooker[34] speaks of _Cycas_ living in the deepest and hottest valleys in Sikkim. _Encephalartos_ is essentially a xerophilous genus. _Stangeria paradoxa_ is said to be confined to forests in Cape Colony, and another species grows among the grass of the Park-lands in open country[35]. While it is true that many Cycads are characteristic of dry regions some species flourish in places where shade and moisture are abundant.